1. Field of the Invention
The present invention relates to a mixed oxide and a coating or a porous material comprising the same. More particularly, the present invention relates to a mixed oxide which can thermally decompose stains which are formed from foods, seasonings and the like to be cooked on cooking utensils, a coating comprising said mixed oxide or a porous material comprising said mixed oxide.
2. Description of the Related Art
U.S. Pat. No. 3,460,523 discloses a coating containing an oxidation catalyst comprising an oxide of zirconium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, tungsten, molybdenum, copper, zinc or a rare earth element, or a noble metal as well as a mixture of the oxide and the noble metal, which catalyst catalyzes the oxidative destruction of the stains of cooked material while heating. The disclosed catalyst accelerates the oxidation of organic materials such as oil, proteins, fats, etc. The suitable ones are oxides of manganese, cobalt, iron, nickel, chromium, tungsten and molybdenum and their mixtures. Among them, the most suitable ones are the compounds in which at least one of the above elements is present in at least two valence states or the compounds in which at least one of the above elements have at least two valence states in a transition period during the oxidation reaction. The above U.S. Patent describes that the coating having the catalytic activity can be obtained by mixing said oxidation catalyst with a silicate such as sodium silicate.
However, the disclosed catalyst has some drawbacks. For example, when a coating is formed from sodium silicate, aluminum phosphate or glass frit and at least one of the oxides of Mn, Co, Fe, Ni, Cu, La and Ce, and salad oil is oxidized on the coating, the coating should be heated at a temperature higher than 400.degree. C. to burn out the oil within one hour while the oil cannot be burnt out at 380.degree. C. within 5 hours. In addition, the coating tends to be flawed.
In the above U.S. Patent, the catalyst comprising 10.33% by weight of manganese, 1.21% by weight of cobalt and 0.72% by weight of nickel was carried on a carrier comprising 47.4% by weight of cerium oxide, 25.4% by weight of lanthanum oxide, 13.9% by weight of neodymium oxide, 5.6% by weight of praseodymium, 6.4% by weight of samarium oxide, 2% by weight of yttrium oxide and 1.7% by weight of gadolinium oxide.